The present invention pertains to an antenna. In particular, a preferred embodiment is an antenna that is integrated into an object while readily and inconspicuously conforming to irregular soft shapes, such as the human body or an inflatable craft.
Antennas, even so-called conformable antennas, are conventionally fabricated using a relatively inflexible base material. That is to say, the base material may be somewhat flexible in one direction or in one plane, but not easily conformable in all three of its dimensions simultaneously and instantaneously. In other words, these antennas would not be suitable for comfortable active wear as an undergarment, for example. Further, should an antenna be desired for incorporation in a relatively soft object such as an inflatable lifeboat or a weather balloon, the rigid nature of conventional antennas could cause unintended damage when the lifeboat or balloon is subject to buffeting, sudden compression, or abrasion.
Another disadvantage of xe2x80x9chardxe2x80x9d portable antennas is that when placed in proximity to the human body, electromagnetic coupling with the body degrades antenna performance. Should one desire to reduce or eliminate this coupling, a relatively large ground plane inserted between the antenna and the body is desirable. Using conventional designs, this ground plane would add unnecessary bulk, weight, and cost while reducing mobility of the human or performance of soft objects such as lifeboats and weather balloons.
There are available specialized fabrics capable of conducting electromagnetic energy. For example, U.S. Pat. No. 4,722,860, Carbon Film Coated Refractory Fiber Cloth, issued to Doljack et al, Feb. 2, 1988 provides an electrically conductive fabric suitable for use at high temperatures such as might be experienced in electric blankets or as screens for microwave ovens. Processes for coating fabric to change its electrical conductivity while retaining flexibility are evidenced in U.S. Pat. No. 5,723,186, Conductive Fabric and Process for Making Same, issued to Fraser, Mar. 3, 1998, and U.S. Pat. No. 5,804,291, same title and inventor as the ""186 patent, Sep. 8, 1998. Further, U.S. Pat. No. 5,906,004, Textile Fabric with Integrated Electrically Conductive Fibers and Clothing Fabricated Thereof, issued to Lebby et al, May 25, 1999, provides electrically conductive clothing.
Additionally, there is specialized clothing incorporating readily apparent (to the naked eye) electrical components such as antennas and radios. See U.S. Pat. No. 4,584,707, Cordless Communication System, issued to Goldberg et al, Apr. 22, 1986, and U.S. Patent 5,884,198, Body Conformable Portable Radio and Method of Constructing the Same, issued to Kese et al, Mar. 16, 1999. Although each of these inventions are at least partially incorporated in clothing, their presence is readily observable due to bulk, configuration, or both. That is, they do not conform to the plane of the cloth in which they are integrated.
Antennas of recent design intended for portability still incorporate inflexible components. For example, see U.S. Pat. No. 5,874,919, Stub-Tuned Proximity-Fed, Stacked Patch Antenna, issued to Rawnick et al, Feb. 23, 1999, and U.S. Pat. No. 5,949,384, Antenna Apparatus, issued to Ikushima, Sep. 7, 1999. The ""919 patent, describes an unconventional design offering performance improvements over existing patch antennas but still incorporating a majority of inflexible components. The ""384 patent provides a flexible portable antenna that has no provision for incorporation in an article of clothing or even in layers of cloth. The ""384 patent provides for a relatively large antenna that can be folded for transportation, but otherwise is not suitable for continuous wear, for example. Both the ""919 and the ""384 patents describe very recent antenna technology for use in small spaces or as a portable device but not entirely suitable for discreet insertion in a piece of everyday apparel.
Consequently, what is needed is a truly flexible antenna, suited to wear as an article of clothing or incorporation in the fabric of an inflatable such as a lifeboat or a weather balloon. The antenna should be low-cost, robust, and provide a sufficiently large ground plane to prevent unnecessary coupling to human or animal bodies. Further, the antenna should be able to be cleaned, using common methods, if provided as an article of clothing. The antenna can be provided with a suitable connector to enable use with a variety of communications, navigation, medical, emergency, security, and rescue systems, as defined by the user. A preferred embodiment of the present invention addresses these needs.
A preferred embodiment of the present invention comprises a flexible patch antenna in a bonded three-layer fabric configuration. A top layer comprises the antenna, a middle layer comprises a dielectric used as an electrical insulator between the top and bottom layers, and a bottom layer comprises a ground plane for the antenna. The three layers are bonded together using a commercial off-the-shelf (COTS) cloth adhesive. In addition, a COTS connector is affixed to the top (non-ground plane) layer for providing electrical communication to a suitable electronic device such as a communications radio or an emergency beacon. Alternatively, the antenna is fed by a miniature waveguide or similar device. The device that will use the antenna is grounded to the ground plane of the antenna, most often through an element of the connector, such as a connection to coax cable shielding.
In a preferred embodiment of the present invention the top and bottom layers are fabricated from a COTS ripstop nylon impregnated with conducting metal fibers, the middle layer is a COTS polyester felt, and the COTS connector is mounted on COTS conducting fabric such as the ripstop nylon of the top layer, and sewn or glued into the top layer. The antenna and ground plane sections are sized to optimize reception/transmission of the operating frequencies of an attached electronic device.
Advantages of preferred embodiments of the present invention, include:
available for use at a variety of operating frequencies;
instantaneously flexible in three dimensions;
greatly reduced coupling to human or animal bodies;
enhanced performance over conventional designs;
increased operational flexibility;
modular and adaptable to a variety of missions;
robust;
cleanable using commonly available methods;
simplified design of alternate configurations using COTS parts;
uncomplicated fabrication;
reduced system bulk, complexity and weight;
reduced capital costs via use of COTS parts;
low maintenance costs;
high reliability; and
ready upgradability.
Embodiments of the present invention can be employed in jackets, shirts, pants, overalls, and other garments. The applications also include sails for sailboats, coverings for non-metallic boats such as wood, fiberglass, or those using a fabric as part of their structure, such as inflatable lifeboats or other small marine craft. It also can be used with hot air balloons, parachutes, weather balloons, flags, wristbands, hats, helmets, integrated security tags, unmanned aerial vehicles (UAVs), combat aerial vehicles (CAVs), hang gliders, and remotely powered vehicles (RPVs). The electronic systems accommodated by a preferred embodiment of the present invention include: emergency locator systems (ELS), communication (COMM) systems, direction finding (DF) systems, global positioning systems (GPS), navigation (NAV) systems, medical identification and monitoring systems (MIMS), and radio location systems (RLS). This configuration saves capital equipment, as well as replacement and maintenance, costs. Further, a preferred embodiment of the present invention may be used in a variety of military, police, rescue, medical, environmental, scientific, security, and commercial roles not enumerated above.
Preferred embodiments are fully disclosed below, albeit without placing limitations thereon.